This invention relates to a sheet capable of releasing a thermal transfer image-receiving layer wherein an image receiving layer on which thermal transfer images have been formed or are to be formed according to thermal transfer recording systems, particularly, according to sublimation thermal transfer systems, is released and transferred on various types of substrates such as polyvinyl chloride sheets or cards and plain cotton cloth sheets. The invention also relates to a method for transferring a thermal transfer image receiving layer and an image-forming method using the release and transfer sheet.
Sublimation transfer recording techniques have wide utility in the fields where video image information is fixed, as a thermal transfer image, on an image-receiving layer of a material to be transferred. The material to be transferred which is ordinarily employed is a printing sheet including a substrate and an image-receiving layer capable of receiving dye images thereon. Using this type of printing sheet, the thermal transfer image is formed by procedures wherein the ink layer of an ink ribbon having thermally diffusable dyes such as disperse dyes therein is superposed on the image-receiving layer of the material to be transferred and heated by heating means, such as a thermal head, in accordance with image information, thereby causing the dye in the ink layer to be transferred to the image-receiving layer. Recently, the images thermally transferred by the sublimation thermal transfer techniques have been formed on various types of materials or substrates. For instance, typical of such a material is a polyvinyl chloride card (hereinafter referred to simply as PVC card) which has an image-receiving layer consisting of polyvinyl chloride. The thermal transfer image is formed directly on the image-receiving layer of the PVC card. Further, attempts have been made wherein a thermal transfer image has been once formed on an ordinary printing sheet which has, on a substrate, an image-receiving layer made of thermoplastic resins and the thus formed image is re-transferred on a plain cloth such as of cotton. In the case, an adhesive sheet made of a thermoplastic resin is sandwiched between the cloth and the image-receiving layer of the printing sheet, followed by hot pressing by use of a warm iron and peeling off the substrate of the printing sheet to re-transfer the image-receiving layer on the cloth. Alternatively, the dye image alone on the image-receiving layer may be re-transferred to an adhesive sheet sandwiched between the cloth and the printing sheet, followed by peeling off the printing sheet to permit the thermal transfer image to be re-transferred on the cloth.
However, when the image-receiving layer on the PVC card on which the thermal transfer image has been formed is brought into contact with materials having large amounts of plasticizers therein, e.g. artificial leathers, soft vinyl chloride sheets, plastic erasers and the like, over a long time, the dye of the thermal transfer image formed on the image-receiving layer is at least partially re-transferred to the material, thereby presenting the problem that the thermal transfer image is damaged. Additionally, ordinarily employed disperse dyes are soluble in organic solvents such as toluene, ethanol and the like. When the image-receiving layer is contacted with such solvents as mentioned above, the dye is dissolved out from the image-receiving layer. This eventually brings about the thermal transfer image being impeded.
On the other hand, with the case of the cloth on which a thermal transfer image has been re-transferred, when the cloth is subjected to dry cleaning, the dye is dissolved out in solvents for the dry cleaning, thus impeding the image on the cloth. With the cloth where a dye image alone is re-transferred to its adhesive layer, dyes have to be used in larger amounts since known disperse dyes are not satisfactory with respect to the transfer efficiency thereof.
Now, there is a demand for readily fixing, as a still image, video information images on various types of substrates other than printing sheets.